[oi-dev] SSD-based pools

[Bob Friesenhahn]

On Tue, 30 Sep 2014, Schweiss, Chip wrote:

> 
> 
> On Tue, Sep 30, 2014 at 11:52 AM, Bob Friesenhahn <bfriesen at simple.dallas.tx.us> wrote:
>
>             Presumably because the checksum is wrong.
> If by turning off 'sync' it is meant that the zil is disabled, then that has nothing to do with zfs checksums being
> wrong.  If drive cache flush is disabled for async transaction groups, then nothing but problems can result (e.g.
> failure to import the pool at all).
> 
> 
> I doubt the pool would ever not be importable.  Data loss sure.  ZFS will be rolled back to the last completed TXG.  Like I
> said before, on this pool data loss is not an issue as long as we know it's lost.   Losing the entire pool because a power
> failure is not an issue.   All the processing pipelines using the pool at the time would have lost power too and would be

Obviously it does happen since there have been reports to the zfs 
mailing list over the years about pools which were completely lost 
because the drive firmware did not honor cache flush requests.

There are only so many (20?) TXG records which are discoverable.

This has nothing to do with zfs tunables though.  Zfs always issues 
drive cache flush requests for each TXG since otherwise the pool would 
be insane.

Bob
-- 
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/